The invention relates to an attenuation arrangement comprising a step attenuator having an input, through which first and second voltage terminals are arranged in cascade with a voltage divider having an output, said attenuation arrangement also comprising a control circuit having a control input for controlling the step attenuator and the controllable voltage divider, the step attenuator having, connected between the input and a reference terminal, a series arrangement of attenuator elements which are connectable in parallel with the two voltage terminals.
Such an attenuation arrangement is known from Dutch patent application No. 300875, which has been laid open to public inspection.
The step attenuator of the known attenuation arrangement distributes an input voltage applied between the input and the reference terminal over the attenuation elements in a plurality of voltage increments. By connecting one of these attenuation elements in parallel with the two voltage terminals, the voltage increment present across this attenuation element is applied to the controllable voltage divider via the voltage terminals. Herein a voltage value located within the range of the voltage increment is connected to the output of the controllable voltage divider.
An increase in the output voltage over the range of the voltage increments of two adjacent attenuation elements is realized in the known attenuation arrangement as follows. After the highest position of the controllable voltage divider has been attained, wherein the highest voltage value of the voltage increment applied between the two voltage terminals is connected to the output, the two ends of the relevant attenuation element are disconnected from the two voltage terminals under the control of the control circuit and the two corresponding ends of the next attenuation element are connected to the two voltage terminals. The controllable voltage divider is now adjusted from the last-mentioned highest position to the lowest position, wherein the lowest voltage value of the voltage increment between the two voltage terminals is connected to the output. The output voltage can now increase further over the range of the higher voltage increment. A decrease of the output voltage over the range of two adjacent attenuation elements is realized by reversing the above method.
The switching actions which must be performed to switch from one voltage increment to the other produce voltage peaks which may become apparent in an unacceptable manner. When this attenuation arrangement is used as, for example, the volume control in wireless sets, these voltage peaks become audible as plopping sounds